show: use the new stack definition for show stack
Now that we have a common stack definition, use it in the hg show stack
command.
Differential Revision: https://phab.mercurial-scm.org/D2397
mercurial (__VERSION__) __CODENAME__; urgency=medium
* Automated build performed by upstream.
-- Mercurial Devel <mercurial-devel@mercurial-scm.org> __DATE__